This is a revised application requested continuation of grant RO1 CA 36622 entitled "Antineoplastic Agents from Marine Organisms." The funding requested is for years 24-28 of the program. The goal of this program, to discover new anticancer agents, has remained the same over the lifetime of the program. However, as the program has matured, the scope of these investigations has been expanded and refocused. The refocusing primarily involves a move away from cytotoxicity screens to mechanism based approaches targeting cellular components or pathways that are either over or selectively expressed in tumor cells versus the normal phenotype. This has been an iterative process over the past 10 years. Screening strategy, development, and results for the past five years will be discussed in the progress report. The expansion of scope has involved investigation of new sources of chemical diversity and an increased emphasis on preclinical development studies of our most promising discoveries. Substantial progress was made in years 19-23 on the specific aims proposed for that cycle. Specifically, samples were collected in Kandavu, Brazil, and Papua New Guinea. These samples were screened in assays at Utah and Wyeth. Isolation and structure determination studies were pursued where appropriate. Significant progress was made in understanding the mechanism of action of neoamphimedine, naamadine A, the patellazoles and lissoclinolide;and p21, p53, PTEN and HIF-1cell based assays were developed and used for screening. These studies are summarized in the progress report. This work has resulted in 42 publications since 2000. Activities in years 23-24 will focus on completion of mechanism of action and in vivo efficacy studies with the patellazoles, lissoclinolide, the punaglandins, the styelsamines, naamadine A and chemical investigations of approximately 400 samples collected in Madang and Milne Bay, Papua New Guinea between October 2003 and July 2005. In years 25-28, we will begin chemical investigations of approximately 150 new organisms per year, which will be collected from a variety of locations in Papua New Guinea including New Ireland, New Britain and the southern fields. These samples will also be prioritized based on results from the screening protocols and dereplication based on taxonomy and LCMS data. Purified metabolites will be further evaluated in secondary assays to define mechanism of action and evaluated for in vivo efficacy.